Congenital antithrombin III deficiency

Venous blood clot

Deep venous thrombosis (DVT) affects mainly the veins in the lower leg and the thigh. It involves the formation of a clot (thrombus) in the larger veins of the area.

Also known as: Deficiency - antithrombin III - congenital and Antithrombin III deficiency - congenital

Definition

Congenital antithrombin III deficiency is a genetic disorder that causes the blood to clot more than normal.

Causes, incidence, and risk factors

Antithrombin III is a protein in the blood that naturally blocks blood clots from forming. Congenital antithrombin III deficiency is an inherited disease. It occurs when a person receives one abnormal copy of a gene from a parent with the disease.

The abnormal gene leads to low levels of antithrombin III. These low levels of antithrombin III can cause abnormal blood clots (thrombi) that may damage organs.

Often, patients with this condition will have a blood clot at a young age and will have a family member who has also experienced a blood clotting episode.

Symptoms

Patients will usually have symptoms of a blood clot, including:

  • Coughing up blood
  • Fainting
  • Shortness of breath and pain when taking deep breaths
  • Swelling of one leg

Signs and tests

A physical examination may show:

  • A fast heart rate
  • A swollen foot or ankle

The diagnosis is made by checking for low levels of antithrombin III in the patient's blood.

Treatment

A blood clot is treated with blood thinning medications or anticoagulants. How long you need to take these medications depends on how serious the blood clot was and other factors. Discuss this with your health care provider.

Expectations (prognosis)

Most patients have a good outcome if they stay on anticoagulant medications.

Complications

Blood clots can cause death, especially if they are in the lungs.

Calling your health care provider

See your health care provider if you have symptoms of this condition.

Prevention

Because this is an inherited condition, there is no way to prevent it. However, once a patient is diagnosed with antithrombin III deficiency, all close family members should be screened.

References

Schafer A. Thrombotic disorders: Hypercoagulable states. In: Goldman L, Ausiello D. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 182.

See also:

  • Test

    Antithrombin III

    Antithrombin III is a blood test that measures the amount of antithrombin III (AT III), a that helps control blood clotting.

  • Disease

    Blood clots

    Thrombus

    Blood clots are clumps that occur when blood hardens from a liquid to a solid. A blood clot that forms inside a blood vessel or within the heart and stays there is called a thrombus. A thrombus that breaks loose and travels from one location in the body to another is called an embolus. The ...

  • Nutrition

    Protein in diet

    Proteins

    Proteins are complex organic compounds. The basic structure of protein is a chain of amino acids.

Review date:
March 2, 2009
Reviewed by:
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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